1. Field of the Invention
The present invention relates to an image forming apparatus which has a maintenance mechanism.
2. Description of the Related Art
In a conventional image forming apparatus of an ink jet system, for example, a recording medium such as recording paper or an OHP sheet is conveyed by a recording medium conveying section. When the recording medium is conveyed, inks are discharged from a plurality of nozzles disposed in a recording head to the recording medium. As is well known, a high-quality image is accordingly formed at a high speed.
In such an image forming apparatus, recording media comes into contact with each other during their conveyance to generate dust such as paper particles. This dust sticks to an ink discharge port of a recording head to cause ink clogging. Bubbles may even enter from the ink discharge port to break ink surface tension. These may cause an ink discharging failure to bend an ink discharging direction.
Thus, a maintenance mechanism has conventionally been essential to quickly eliminate the aforementioned causes together with a recording system such as an ink jet system.
As recording systems, there are available a system of performing recording while moving both of a recording head and a recording medium, and a line head system which has, e.g., a recoding head fixed to a line head, and conveys a recording medium only to perform recording.
In the case of the former recording system, the recording head is small, and a maintenance mechanism is small.
However, in the case of the latter line head system, a length of the recording head must be equal to a width of the recording medium, and a maintenance mechanism becomes large when a recording head of plural colors is disposed. In a position facing the recording head, a recording medium conveying section for conveying the recording medium is disposed. Accordingly, the maintenance mechanism must retreat from the position facing the recording head during recording.
As retreating mechanisms, for example, there are known a method of retreating a maintenance mechanism in a direction orthogonal to a recording medium conveying direction with respect to a recording head group in which recording heads of plural colors are arrayed, and a method of retreating a maintenance mechanism below a recording medium conveying section during recording, and sliding the recording medium conveying section during maintenance.
Jpn. Pat. Appln. KOKAI Publication No. 2005-022182 discloses an example of such a retreating mechanism. An ink jet printer shown in FIG. 18A includes a recording medium conveying mechanism 120 for conveying a recording medium (not shown), an ink jet head 112 for discharging an ink to the recording medium conveyed by the recording medium conveying mechanism 120 to form a desired image, a maintenance unit 140 for performing a recovery operation for the ink jet head 112, a retreating mechanism (not shown) for sliding (horizontally moving) the recording medium conveying mechanism 120 to retreat from a space between the ink jet head 112 and the maintenance unit 140 during the recovery operation as shown in FIG. 18B, and a moving mechanism (not shown) for moving at least one of the ink jet head 112 and the maintenance unit 140 for performing the recovery operation to a recovery operation position.
However, according to the aforementioned mechanism, as shown in FIGS. 18B to 18D, the recording medium conveying mechanism 120 must move in the recording medium conveying direction, i.e., in the horizontal direction. Thus, a space equal to or larger than a size of the recording medium conveying mechanism 120 is necessary in the recording medium conveying direction. As a result, an apparatus becomes a large and expensive mechanism.